1. Field of the Invention
The present invention relates to devices for controlling and monitoring processes. In particular, the devices may be used for the process control and monitoring of engine exhaust treatment systems.
2. Description of the Related Art
An internal combustion engine generates exhaust gases that includes components that are regarded as pollutants, such as carbon monoxide (CO) and oxides of nitrogen (NOx). Many engines are fitted with an exhaust treatment system to reduce the exhaust gas pollutants emitted by the engine. Exhaust treatment systems that are retrofitted to an in-use engine can be passive or active in nature. Typically, passive exhaust treatment systems are simply connected to the engine exhaust stream and cannot respond to unusual conditions outside of their design parameters.
An example of a passive system is a diesel particulate filter (DPF) such as the “CRT” (Continuously Regenerating Trap) particulate filter product available from Johnson Matthey of Malvern, Pa., USA. A DPF places a filter in the path of the exhaust stream to trap pollutants that would otherwise be released as part of the exhaust. These types of exhaust treatment systems typically require periodic maintenance and in some instances might require immediate attention to maintain proper operation (i.e., effective exhaust treatment). Therefore, it is necessary to continuously monitor the engine exhaust gas components during engine operation. An active system, for example, a DPF with exhaust brake, a DPF with reagent injection, or a lean NOx catalyst with reductant reagent injection, requires a controller for proper function.
The Johnson Matthey company provides a “CRTdm” (CRT Filter diagnostic module) product, a monitoring apparatus for particulate filters. The “CRTdm” has two inputs (a thermocouple and an analog voltage), four LED outputs, and includes a data logging capability. The “CRTdm” apparatus, however, does not allow control of an injector or valve.
In addition to system monitoring, it is also important to record engine operating conditions for future analysis and to provide information for troubleshooting malfunctions. For example, if a DPF is approved for application on a vehicle with a duty cycle that results in high exhaust temperature, but the vehicle is operated under a duty cycle with significantly colder exhaust temperature, a record of the engine operating conditions, such as a data log, would document the out-of-specification operating conditions. In addition, the data log may be used to document the regularity of scheduled maintenance.
National Instruments Corporation of Austin, Tex., USA has a line of data acquisition and control systems that is generally flexible and programmable (viewable on the Internet “World Wide Web” at the URL of www.ni.com). The systems, however, tend to be relatively expensive, complex, and generally require a personal computer to operate. For example, National Instruments Corporation provides a “LabVIEW” software product that supports development of measurement and control applications using a graphical user interface. The software runs on a personal computer and contains various modules for data collection, instrument input/output, and data processing. One of the modules provides a histogram tool, as described in “LabVIEW Statistical Process Control Tools” User Guide, document 322042A-01.
U.S. Pat. No. 5,373,733 to Fuchs et al. entitled “Exhaust filter backpressure indicator”, indicated as assigned to Donaldson Company, Inc. of Minneapolis, Minn., USA, describes an exhaust filter backpressure indicator that includes a sensor for measuring the backpressure and the exhaust system. The sensor sends a signal that is processed for indicating that an exhaust filter element is filled. The indicator operates according to engine operating speeds (RPM) and according to exhaust back pressure. There is no description of any data logging function.
U.S. Pat. No. 6,234,176 to Domac et al. entitled “Data logger for transportable life support system”, indicated as assigned to Integrated Medical Systems, Inc., of Greenwich, Conn., USA, describes a technique for logging information representative of the operation of medical devices, such as those of a transportable life support system. The technique includes isolation circuitry designed to mitigate electronic interference with the medical devices.
U.S. Pat. No. 5,564,285 to Jurewicz et al. entitled “Method of converting a time based data logger to a time and random event based data logger” is indicated as assigned to Thermo King Corporation of Minneapolis, Minn., USA. The Jurewicz patent describes a method of processing data logger inputs to allow both asynchronous logging of data (i.e., event-based data such as equipment malfunction) and also synchronous logging of data (i.e., time-series data stored at predetermined constant time intervals).
U.S. Pat. No. 5,623,416 to Hocker entitled “Contact closure data logger”, indicated as assigned to Onset Computer Corporation of Pocasset, Mass., USA, describes a contact closure data logger that monitors state changes in a main switch, and records the time at which the state changes occur. Operational features to conserve power are included. The logger is described in the context of energy usage monitoring and for use with tipping bucket rain gauges.
U.S. Pat. No. 6,144,717 to Rodrigues entitled “Wheel mounted data logger” describes a wheel mounted data logger with an odometer for mounting at a hub of a wheel of a vehicle and response to turning of the wheel, an hour meter for mounting on a structure of the vehicle and response to running of an engine of the vehicle, and microcontroller for mounting on the vehicle and receiving, recording and transmitting the responses of the odometer and hour meter. The wheel logger obtains information about operation of the vehicle to which it is mounted.
U.S. Pat. No. 4,817,118 to Wilburn et al. entitled “Mobile incident logger”, indicated as assigned to Step Engineering of Sunnyvale, Calif., USA, describes a mobile incident logger for monitoring an on-board, automotive, computer and signal levels developed by analog and digital sensors, the logger employing a coverage monitor, which records which memory locations are accessed by the computer; a cycle tag counting unit, which counts bus cycles of the computer; a discriminator, which detects the occurrence of incidents the logger is to record; a trace memory unit, which stores bus states of the computer; a trace memory unit, which stores memory variables of the computer; a discriminator, which detects the occurrence of some of the incidents the logger is to record; and a trace memory unit, which stores the sensor signals.
German Patent Application No. 36 09 428 is directed to “A Method and a Device for Testing Devices of a Motor Vehicle for a Fault-Free Condition”. The application discloses the detection and storing of faults, both with respect to the input and output signals, as well as to the internal signal processing of a control unit, and the outputting of the same in response to a request signal. Specifically, the memory, into which possible fault signals are written, is queried on a block by block basis in response to a request signal and, moreover, there is a ranking of the faults when they are output to the display.
German Patent Application No. 40 38 972 is directed to a “Device for Computing a Motor-Vehicle Service Interval”. It provides for various operational values to be recorded, such as number of starts, crankshaft revolutions, driving and parking times, engine temperature, engine oil pressure and the like, and for the service interval to be calculated from the values by a computer.
Several commercially available data loggers are known, including the Pace Scientific Pocket Logger, the Onset Computer HOBO, Omega data loggers, and loggers from Campbell Scientific.
Another important function to be performed is that of actively controlling a process. For example, an active exhaust treatment system might include components that adjust engine operation to achieve a desired exhaust emissions characteristic or otherwise adjust system operation to be within predetermined operating parameters. Such adjustments can be initiated by an appropriately designed controller.
There are many controllers for engines and engine exhaust aftertreatment systems. Some systems involve fitment of selective catalytic reduction (SCR) systems and have controllers that monitor the engine and aftertreatment system, and also control the injection of a reducing agent. Examples of manufacturers who provide such SCR systems include HUG Engineering AG of Räterschen, Switzerland and Siemens AG of Regensburg, Germany. Such systems can be both mobile and stationary.
In addition to engine and engine exhaust treatment systems such as described generally above, other industrial processes would benefit from improved monitoring, logging, and control. Such processes can include, for example, chemical plants, fuel processing plants, and the like.
Because data logging can require a relatively large amount of data storage space, efficient data recording can be important. Commercially available data loggers and data acquisition systems typically use constant logging intervals (e.g., record the sensor values every 10 seconds until the user chooses another value). The use of a constant logging interval is highly inefficient for data logging of vehicles because there are many time periods where sensor values do not change. For example, a truck driving at a steady speed on the open highway, or a bus stopped and waiting to run to the next route repetition, will both exhibit little change in their operating conditions and sensor values.
Thus, there is a need for combinations that provide monitoring, logging, and control functions and that can be easily fitted to systems. In addition, there is a need for efficient recording of system data for such combinations. The present invention satisfies these needs.